Dual-isotope SPECT using (99m)Tc-hydroxymethylene diphosphonate and (201)Tl-chloride to assess mandibular invasion by intraoral squamous cell carcinoma.

Unlabelled: We examined mandibular invasion of intraoral squamous cell carcinoma by simultaneous bone and tumor dual-isotope SPECT using (99m)Tc-hydroxymethylene diphosphonate ((99m)Tc-HMDP) and (201)Tl-chloride ((201)Tl) and by CT.

Methods: Early and delayed simultaneous bone and tumor dual-isotope SPECT and CT were performed on 39 patients suspected of having tumor invasion of the mandible by intraoral squamous cell carcinoma. SPECT images were superimposed to project tumor location from tumor SPECT onto the osseous structures shown by bone SPECT. The CT imaging protocol consisted of 5-mm contiguous axial images.

Results: Histopathologic examination revealed invasion of the mandible in 13 patients and no tumor invasion in 26 patients. The results of delayed dual-isotope SPECT were exactly the same as those of early dual-isotope SPECT. On early and delayed dual-isotope SPECT, the sensitivity, specificity, and accuracy in detecting mandibular invasion by intraoral squamous cell carcinoma were 100% (13/13), 88.5% (23/26), and 92.3% (36/39), respectively. The corresponding values using CT were 45.5% (5/11), 94.7% (18/19), and 76.7% (23/30), respectively, when 9 patients were excluded because of dental artifacts.

Conclusion: Our results suggest that superimposed early bone and tumor dual-isotope SPECT images alone may be sufficient in the diagnostic evaluation of mandibular invasion by intraoral squamous cell carcinoma.